1. Technical Field
The present invention relates to a disk for audio data, reproduction apparatus, and method of recording/reproducing audio data.
2. Related Art
One of conventional recording mediums for memorizing audio data is a compact disk (CD), which is categorized into optical disks for reproducing audio data. A digital versatile disk (or a digital video disk) (DVD), which is also a conventional recording medium, is known as an optical disk higher in recoding density than the CD.
In such conventional conditions, the DVD (hereinafter referred to as “DVD-Video”) records thereon video signals as a main signal and audio signals as a subsidiary signal. Thus this recording scheme has the problems described below.
First, the audio signal is combined with the video signal in the DVD-Video, so that a capacity for recording the audio signal is limited to a small amount. Secondly, it is impossible to manage time for recording the audio signal independent of the video signal. Thirdly, audio data cannot be recorded in a high grade manner and lossless compression cannot be applied to recording audio data.
Also, since compared to video users, audio users range over various ages, it is requested that the DVD-Video provide a simplified reproduction way realized by using a TOC (table of contents), as can be seen in the CD. However, in using a reproduction apparatus such as player whose recording medium is the DVD-Video, a navigation control pack (called “CONT pack”) is combined with plural video (“V”) and audio (“A”) packs so as to form a video contents block unit that is in charge of controlling the reproduction of the “V” and “A” packs. Therefore, for users who desire to record and reproduce audio signals in the DVD-Video disk independent of the video signal, it is difficult to primarily record and reproduce them in a simple manner, thus resulting in that the DVD-Video disk is not very useful for users.
Moreover, in the case of using the DVD-Video, the time management is dependent on only intervals of video frames. This will cause a difficulty when a user desires to primarily record audio signals. That is, it is difficult to manage the audio signals in real time, although continuously playing back is more significant for the audio signals than video signals.
In order to ease such a difficulty, some techniques of improving the continuity of audio signals have been proposed. One of such techniques is shown by Japanese Patent Laid-open publication No. 11-185450, in which there is disclosed an encoder that allows a user to easily reproduce audio signals, thus having a good usability, and to easily manage the real-time performance of recording of audio signals. Another technique is shown by Japanese Patent Laid-open No. 2002-358732, which provides a recorder for disks in which audio data for a longer period of time can be recorded in a compressed manner. This recorder is therefore useful for alleviation of a problem that some compression techniques such as AAC (Advanced Audio Coding) and AC-3 (Dolby AC3), which are effective in saving a memory capacity for audio signals, cannot be applied to compressed audio signals.
However, the above conventional encoder and recorder still face some drawbacks which have not been resolved fully yet. Specifically, the above-described encoder and recorder are not sufficient in that audio data cannot be recorded both in a high grade manner with lossless compression and in a reasonable grade manner with lossy compression. In addition, the above-described encoder and recorder cannot cope with providing various types of compressed audio data with a various range of recording time. In the above-described encoder and recorder, there is still a problem that a user cannot chooses a desired type of compressed audio data according to the category of the music or user's recording medium.